Apparatus for forming fibers



March 5, 1968 w. F. PORTER 3,372,011

APPARATUS FOR FORMING FIBERS iled June 7, 1965 W/LL/AM F PORTER I N VEN TOR.

ATTORNEY United States Patent 3,372,011 APPARATUS FGR FORMING FIBERS William F. Porter, Roselle, lll., assignor to United States Gypsum Company, a corporation of Delaware Filed June 7, 1965, Ser. No. 461,736 3 Claims. (Cl. 65-14) ABSTRACT on THE DISCLOSURE Apparatus for forming fibers comprising a rotor having orifices in its side Wall, a surrounding ring burner, a streamlining cone extending downstream from the rotor, and an attenuating blast ring located donwstream from the rotor at distance equal to or greater than about /2 the diameter of the rotor. The attenuating blast ring has an inside diameter about equal to the outside diameter of the rotor, and the attenuating blast from this ring is directed axially downstream from the rotor.

This invention relates to an apparatus and method in which fibers are initially formed on a heated centrifugal rotor and subsequently attenuated by a supplemental current or blast of gas.

In forming glass fibers through the use of a centrifugal rotor having a perforate wall, it is quite well known to employ burners to maintain the rotor at operating temperature and also to supply an environment at elevated temperatures in which the diameter of the fibers may be reduced. To satisfy demands for fibers of smaller diameter and to increase the production rate of very fine fibers, it has become customary to employ secondary attenuating means.

It is an object of this invention, therefore, to provide an improved secondary attenuating means for producing very fine glass fibers. It is a further object of this invention to provide a secondary attenuating means which is efficient and economical in its operation.

It is a still further object of this invention to provide a process for attenuating glass fibers formed on a centrifugal rotor.

Other and more specific objects and advantages of the invention will appear by reference to the drawing and specification which follow.

In general, the objects of this invention are achieved by the provision, downstream from the fiberizing rotor and its associated heat supply, of a fiber attenuating, high velocity gas source which may conveniently be a ring having an inside diameter about equal to the outside diameter of the rotor, although it may be slightly larger or smaller for certain applications. The distance downstream from the rotor should be equal to about one-half the diameter of the rotor but this may be somewhat less or considerably more depending upon the particular installation.

In operation, the centrifuge is rotated at high speed and its periphery is heated by combustion products issuing from an encircling burner. Glass fibers are drawn from the rotor through the heated environment and are carried downstream from the burner by the current of combustion products. The path of hot gases from the burner tends to follow the surface of the rotor and so constrict the stream of fibers. This constricted stream is then passed through an attenuating ring which imparts a blast of high velocity gas coaxially and codirectionally onto the fiber stream.

The construction and operation of the attenuating apparatus will be better understood through reference to the drawing which illustrates one embodiment having a fiber forming rotor I mounted on a shaft 2 which is adapted for rapid rotation by means not shown. The rotor is in the form of a shallow cup having a side wall 3 which contains a larger number of fiber forming orifices 4. Surrounding the rotor is a ring burner generally indicated at 5 which comprises a combustion chamber 6 defined by metal walls 7 and a ceramic lining 8. A manifold 9 is arranged to supply premixed fuel and air under pressure to the burner through a plurality of supply pipes 10, some of which have not been shown for clarity of illustration. The mixture is burned in the chamber 6 and the combustion products discharged in a high velocity, high temperature current through the discharge port 11 where they are directed across the wall 3 of the rotor. A cone 20 secured to the bottom of the rotor assists in reducing the diameter of the stream of eflluent combustion products.

The attenuating ring 30 is located downstream from the rotor and coaxial with it. This ring has an interior passage 31 adapted to convey a high pressure fluid such as steam through a plurality of orifices 32 from which it is directed axially downstream from the rotor as high velocity annular blast. In some embodiments the blast may comprise combustion products, compressed air and the like.

In operation, the rotor is revolved at high speed and its rim 3 brought to nearly operating temperature by the combustion products discharged through the slot 11 and with supplemental burners within the rotor but not shown. A stream of molten glass 40 is directed into the interior of the centrifuge so that centrifugal force expels the glass melt through the orifices 4 to form fibers 41 which are swept downstream in proximity to the wall of the cone 20 and through the interior of the ring 30. As the stream of fibers passes through the ring, a high velocity blast is directed upon it from the apertures 32 in the form of high speed jets 33. The action of the combustion products upon the fibers when they are first formed at the orifices 4 reduces the diameter to such an etxent that for some purposes, they are satisfactory. The action of the attenuating blast 33 is to further reduce the diameter of the fibers so that they are suitable for those applications which are more exacting and demand a fiber of very small diameter.

In the embodiment illustrated, the rotor was about 11 /2" in diameter and was provided with fiber forming orifices from 0.025 to 0.030 inch in diameter. A stream of molten glass at a rate of about 500 to 1,500 pounds per hour was supplied to the interior of the centrifuge where the high speed rotation caused it to be thrown or forced through the orifices, forming fibers which, however, are much smaller than the orifices themselves. The hot gases issuing from the burner served to attenuate fibers to maintain their temperature and to carry them downstream to the attenuating ring.

This ring had an inside diameter of about 12" and was placed about 9" downstream from the bottom of the rotor. Steam at 50 pounds per square inch was supplied to the chamber 31 and issued from apertures 32 as high velocity jets which were directed coaxially with the stream of fibers. The fibers collected downstream from the attenuating ring showed a rather uniform distribution of sizes in a range from about one to about ten microns in diameter with a mean at about six microns. A sample taken of the fibers just before they entered the attenuatmg ring showed that their diameter was approximately twice this value, ranging from two to about twenty microns with a mean between about eight to about 12 microns.

The attenuating ring was positioned as close as 5" to the bottom of the rotor and more than 12" downstream and was found to operate satisfactorily throughout this range.

The mechanism by which the steam ring located in this position operates to reduce fiber diameter is not clearly understood. It may be that the burner combustion products, somehow aided by the steam, have an opportunity to attenuate the fibers more effectively. It may also be that the smaller diameter of the steam ring which this combinationm'akes possible provides for a more concentrated application of energy to the fibers so that greater efi'lciencyresults Whatever the mode of operation, it has been established that this is a highly effective and useful methodand apparatus for forming glass fibers of small diameter.

It is understood, of course, that this invention is not to be limited to the particular embodiment shown and described above, since many modifications may be made, and it is contemplated by the appended claims to cover such modifications as fall Within the true spirit and scope of thisinv'ention.

What is desired to be claimed is:

1. Apparatus for forming fibers comprising a rotor including a side wall having a plurality of fiber forming orifices therein, said rotor having an upstream side and a downstream side, a shaft supporting said rotor and extendingon the upstream side thereof, burner means coaxialwith and encircling said side wall, and attenuating ring means coaxial with and downstream from said rotor, said attenuating ring'means having an inside diameter not substantially larger than the outside diameter of the rotor,

and said attenuating ring means including gas discharge means disposed to direct a blast of gas downstream from said rotor substantially parallel to the extended axis of said shaft.

2. Apparatus for forming fibers as in claim 1 wherein said attenuating ring means is positioned downstream from the bottom of said rotor a distance equal to from about /2 to about 1 rotor diameter.

3. Apparatus for forming fibers comprising a rotor including a side wall having a plurality of fiber forming orifices therein, said rotor having an upstream side and a downstream side, a shaft supporting said rotor and extending on the upstream side thereof, burner means coaxial with and encircling said side wall, conical streamline means associated with said rotor and e xtending downstream therefrom, and attenuating ring means coaxial with and positioned downstream from the bottom of said rotor a distance equal to from about /2 to about 1 rotor diameter, said attenuating rin-g means having 'an inside diameter not substantially larger than the outside diameter of the rotor and including gas discharge means disposed to direct a blast ofgas downstream from said rotor substantially parallel to the extended axis of said shaft.

References Cited UNITED STATES PATENTS 3,014,235 12/1961 Snow 65-6 3,285,723 11/1966 Levecque et a1. 65--6 DONALL H. SYLVESTER, Primary Examiner.

R. L. LINDSAY, Assistant Examiner. 

